This invention relates to a thread cutter milling tool usable to form internal or external screw threads on a workpiece. The principal feature of the invention is the fact that the cutter body (insert) has two sets of cutter teeth oriented symmetrically to the central axis of the cutter body, whereby the useful life of the cutter is essentially doubled. The cutter body can be oriented with either set of cutter teeth presented to the work surface.
Each set of cutter teeth is formed by a series of serrations in a longitudinal edge surface of the cutter body. Recesses are formed at the junctures between the major faces of the cutter body and respective ones of the serrated edges on the cutter body. Each recess forms a cutter surface set back from the associated major face of the cutter body; each recess also forms a chip breaker surface extending generally transverse to the respective major face of the cutter body.
The respective chip breaker surfaces are symmetrical to the central longitudinal axis of the cutter body, whereby the cutter body can have two different positions of adjustment on the associated shoulder, with one of the chip breaker surfaces presented to the work for chip breaker action, and the other chip breaker surface being engaged with a longitudinal shoulder formed on the holder for rigidly orienting (positioning) the cutter body on the holder.
A major feature of the invention is the recess construction in the cutter body whereby either one of the chip breaker surface can perform a chip breaker function while the other chip breaker surface acts as a cutter body orientation device. The non-cutting cutter surface faces away from the work so that it is protected from possible damage by the chips during normal machine operation.
In some respects the tool of this invention is similar to a tool shown in U.S. Pat. 4,531,863 issued to Smith. The Smith patent shows a cutter body (insert) having multiple sets of cutter teeth and intervening flat surfaces, whereby the cutter body can have different orientations on the associated holder. The Smith patent however does not show the use of chip breaker surfaces as orientation devices for the cutter body.